1. Field
The present invention relates to a system and a method for adaptively controlling the temperature of a vehicle's battery when the vehicle is travelling along a known route.
2. Description of the Related Art
Most vehicle batteries that are used to power hybrid and electric vehicles are designed to operate at a pre-determined operating temperature range. Typically, a temperature sensor is attached to or integrated with the vehicle batteries to measure the current temperature of the vehicle batteries. The batteries generally discharge electricity when the vehicle is accelerating and the batteries are charged with electric power that is recovered when the vehicle is decelerating, sometimes referred to as regenerative braking. The battery can also be charged with electric power that is recovered during the vehicle deceleration. These discharging and charging cycles are repeated during travel of the vehicle, which can cause a temperature of the battery to increase. When the temperature of the battery is higher, an internal resistance of the battery is lower and the efficiency of charging and discharging is increased.
When the temperature of the vehicle batteries fall outside the normal operating temperature range, the vehicle electronics usually activate a cooling device (e.g., a fan) or a heating device (e.g., a heater) to adjust the temperature of the vehicle batteries so they are operating within the normal operating temperature range.
However, when the battery temperature goes above a certain level, it may cause the battery electrolyte to degrade. As a result, the efficiency of charging and discharging the battery may be reduced. Therefore, it is desirable to keep the battery at an efficient operating temperature that is below the level at which the battery electrolyte degrades. To address this issue, Japanese Pat. Pub. No. 2005-63689A discloses a method of cooling the battery by using a cooling fan driven by an electric motor when the battery temperature exceeds a threshold temperature.
According to the prior art method, by cooling the battery so as to keep the battery temperature below a threshold temperature, the battery charging and discharging efficiency degradation that can occur at the higher battery temperature may be reduced. However, there is still room for improvements. In the prior art method, the threshold temperature to cool the battery is fixed. This can cause the cooling fan to be operated more often than is needed to keep the discharging and charging efficiency close to an optimal efficiency. On the other hand, this can cause the cooling fan to operate less during other conditions, depending on the threshold temperature setting. Also, more energy may be consumed to drive the cooling fan. Or, the battery temperature may increase more than desired, and the efficiency of charging and discharging may be degraded. As a result, the overall efficiency of the electric system may be degraded.
Thus, there is a need for systems and methods, and/or devices, for adaptive battery temperature control of a vehicle over a known route.